diff --git a/changes-5.1.html b/changes-5.1.html
index 7b0ad0fd0..66d58d915 100644
--- a/changes-5.1.html
+++ b/changes-5.1.html
@@ -16,8 +16,9 @@
 
 <h2>Yap-5.1.2:</h2>
 <ul>
+<li> NEW: with_mutex/2.</li> 
 <li> NEW: call_cleanup/2 and call_cleanup/3 at the request of Paulo
-Moura and Christian1.</li> 
+Moura and Christian.</li> 
 <li> FIXED: garbage collector would not understand bindings to mavars in
 tabling version.</li> 
 <li> FIXED: cut might not prune correctly around meta-call (obs by
diff --git a/pl/threads.yap b/pl/threads.yap
index adad8ae58..8d2b0d88b 100644
--- a/pl/threads.yap
+++ b/pl/threads.yap
@@ -335,7 +335,28 @@ mutex_unlock_all.
 	NRefs > 0,
 	'$unlock_mutex'(Id),
 	'$mutex_unlock_all'(Id).
-	
+
+with_mutex(M, G) :-
+	var(M), !,
+	'$do_error'(instantiation_error,with_mutex(M, G)).
+with_mutex(M, G) :-
+	var(G), !,
+	'$do_error'(instantiation_error,with_mutex(M, G)).
+with_mutex(M, G) :-
+	\+ callable(G),
+	'$do_error'(type_error(callable,G),with_mutex(M, G)).
+with_mutex(M, G) :-
+	atom(M), !,
+	(	recorded('$mutex',[M|Id],_) ->
+		true
+	;	'$new_mutex'(Id),
+		recorda('$mutex',[M|Id],_)
+	),
+	'$lock_mutex'(Id),
+	call_cleanup(once(G), '$unlock_mutex'(Id)).
+with_mutex(M, G) :-
+	'$do_error'(type_error(atom,M),with_mutex(M, G)).
+
 current_mutex(M, T, NRefs) :-
 	recorded('$mutex',[M|Id],_),
 	'$mutex_info'(Id, NRefs, T).